This invention relates to propellants useful in the art of firearms, munitions, pyrotechnics, and the like, and particularly relates to gas-forming, deflagrating compositions and methods for their production.
Black powder is the name applied to deflagrating compositions consisting essentially of an intimate mixture of potassium nitrate, sulfur and charcoal in the approximate proportion 75:10:15. Other than minor variations which have been made to produce certain desired effects, this general composition has not changed since about 1560. Black powder has largely been replaced by smokeless powder as a propellant for firearms ammunition, primarily because the latter is safer to handle and store and does not produce "fouling" or corrosion of the firearm which are both characteristic of black powder. However, the gas pressures produced by the burning of smokeless powders are many times greater than those produced by black powder, and as a result, smokeless powder requires a considerably stronger firearm and also much more care in the amount of propellant used in order that dangerous pressure levels are not produced.
The art has long sought a deflagrating propellant composition which combines the low pressure characteristics of black powder and the safe handling and storage properties of smokeless powder.
A further undesirable characteristic of black powder is the composition of its combustion products. A desirable propellant yields a very high percentage of low-molecular weight gases in its combustion products in order to impart the most efficient propulsion to a projectile. Upon combustion, black powder characteristically produces about 43 percent of gas, 56 percent of solids, and about 1 percent of water vapor. The large amount of solid combustion products results in poor efficiency and in the copious quantities of smoke which is characteristic of black powder. The combustion products of smokeless powder, on the other hand, are almost entirely gases which are useful for efficient propulsion.
Yet another disadvantage of black powder resides in the extremely heavy and expensive equipment required in its manufacture. Thus, the composition is commonly mixed, milled under massive stone wheels, pressed in a hydraulic press at about 1200 p.s.i., granulated by crushing the presscake, and then polished and graded. The multi-step operation requires not only considerable expense in investment for equipment, but also it is time-consuming and extremely dangerous in its operation. Thus, the art is in need of a simpler, less expensive, and safer method to produce deflagrating compositions of the lower-pressure, or "black powder" type.
An important characteristic of propellants which determines their usefulness in the firearms art (including small arms, artillery, and kindred military weapons) is its rate of burning. The U.S. Army Ordnance Corps has shown that such propellants are required to burn rather slowly in order not to produce excessive pressures in the bore of a gun. The pressure must be sufficient to impart desirable velocity to the projectile and not drop too rapidly as the projectile travels toward the muzzle.
The advantage offered by our compositions is their unique property of imparting high velocity to a projectile within a firearm or the like without the concomitant development of dangerously high pressure within the chamber. It is known in the art that the muzzle velocity of a bullet or similar projectile leaving the barrel of a firearm is proportional not to the peak pressure developed within the bore, but rather to the integrated area under the pressure-time curve. [See "Modern Pressure Measuring" by Dan Pawlak, HANDLOADER Magazine, Volume 9, Number 6 (1974) pp 26 ff.]
Although the art has long sought propellant compositions which impart high velocities without the high pressure characteristic of smokeless powder, no commercially acceptable substitute for the well-known "black powder," without its inherent disadvantages discussed above, has heretofore been found.